For example, in a motor mounted on a vehicle such as an automobile, an insulation displacement terminal is used for electrical connection between a winding of a stator and a control substrate. For example, as shown in US 2001/0039139 A1, this type of insulation displacement terminal is configured by a plate-like metal part having spring properties and having a slot for fitting. The electrical wire with an insulation coating is inserted and fitted into the slot, and both side portions of the slot of the metal part are pressed to a conductor of the electrical wire so as to cut the insulation coating. As such, an electrical connection is obtained. In this case, since contact resistance with the electrical wire needs to be lowered, a spring force of the insulation displacement terminal is increased to obtain a large fitting force (e.g., contact load) on the electrical wire.
The fitting force of the insulation displacement terminal is obtained by using an internal energy to return to the original shape, for example, which is observed in metal or resin. In this case, stress relaxation phenomenon occurs in which stress (e.g., fitting force) decreases with time elapsed after fitting. The contact load to the electrical wire gradually decreases, and, finally, necessary fitting force cannot be obtained and the insulation displacement terminal cannot sufficiently function. In particular, this stress relaxation phenomenon is accelerated as an ambient temperature increases. Even when the lifetime of the insulation displacement terminal is sufficiently long in normal temperature, there is a possibility that a desired lifetime cannot be achieved when the insulation displacement terminal is used under high temperature environment.